A screensaver's a type of computer program initially designed to prevent "Phosphor burn-in" on CRT and plasma computer monitors by blanking the screen or filling it with moving images or patterns when the computer isn't in use. Contemporary screensavers are used primarily for entertainment or security. Purpose Before the advent of LCD screens, most computer screens were based on cathode ray tubes (CRTs). When the same image's displayed on a CRT screen for long periods of time, the properties… (More on Screensaver)